This invention relates to a system for sorting elongated members in which the pieces are successively conveyed by a conveyor means are detected as still images by an industrial television camera, and the image signal of the television camera is processed to determine whether each piece is an acceptable one or an unacceptable one and to sort out each piece according to the size. Typical pieces are vegetables such as asparagus, celery, mushrooms, carrots, and the like. The invention will be described with respect to asparagus, but is not so limited in utility.
For agricultural products such as asparagus, it is necessary to sort a large number in a short period of time to keep them fresh. However, heretofore a large number of pieces of asparagus are visually inspected by an inspector to sort them. Since the speed at which the inspector visually inspects pieces of asparagus conveyed by the conveyer is limited, it is difficult to visually inspect a large number of pieces of asparagus in a short time. Furthermore, since there are individual variations in sorting criteria among inspectors, different inspectors may have different inspection standards. Therefore it is difficult to inspect all of pieces of asparagus according to the same inspection standard. In order to eliminate the above-described inspection errors, it is necessary to provide inspectors who can inspect according to one and the same inspection standard. However, it is not practical such subjective judgements must be made.
In order to eliminate the above-described difficulties accompanying the conventional visual inspection performed by human inspectors, a method may be considered in which a detector such as a photo sensor and a limit switch is employed to measure asparagus length and asparagus stem diameter. However, in this method, if the detector is fixedly provided, each piece of asparagus to be conveyed by the conveyer means must be placed at a predetermined position on the conveyer. For this purpose, the conveyer must be designed so that pieces of asparagus are placed correctly at the predetermined positions on the conveyer means, then conveyed, and detected by the detector. Thus, the method is disadvantageous in that the design of a suitable conveyer is exceptionally difficult.